Reinforced structural assembly

ABSTRACT

A stiffener is provided for reinforcing a hollow structure having a pair of spaced walls. The stiffener includes a carrier member with a layer of expandable polymer which creates a structural foam when the polymer is later expanded. The stiffener could comprise a single laminate shaped to fit in the appropriate locations of the hollow structure so that when the polymer is expanded it forms a structural foam intimately bonded to the pair of spaced walls. The stiffener may also be in the form of a corrugated frame wherein individual laminates are provided with notches to permit the individual laminates to be interlocked with each other at the notches.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon provisional application Serial No.60/133,375, filed May 10, 1999 and is a continuation in part ofapplication Ser. No. 09/236,917, filed Jan. 25, 1999.

BACKGROUND OF THE INVENTION

In various practices it is desired to reinforce a hollow structuralassembly, particularly structural members or sections which aresubjected to edge or in-plane stresses which would tend to cause thestructural member to buckle. Frequently holes are formed in structuralmembers in order to weld internal reinforcements. Where, for example,the structural member is made of steel, a reinforcement is then weldedto the structural member to prevent buckling. The holes would then becovered with cloth or plastic for appearance purposes.

It would be desirable if such hollow structural members could bereinforced by placing a reinforcement insert assembly into the hollowstructure between the spaced walls in such a manner that would avoid theabove problem. Typical applications for such practices could be in theautomotive field, such as for reinforcing pillars. Other practices couldbe in the furniture field, such as for office furniture end shelvingunits where shelves are locked into vertical end walls or panels.

SUMMARY OF THE INVENTION

An object of this invention is to provide a reinforced structuralassembly which meets the above needs.

A further object of this invention is to provide such a reinforcedstructural assembly which includes a stiffener capable of being readilyplaced into the assembly.

A still further object of this invention is to provide techniques forreinforcing a structural assembly.

A further object of this invention is to provide such practices whichcould be used for various applications, such as in the automotive fieldor in the furniture reinforcement field.

In accordance with one embodiment of this invention a stiffener isformed by interconnecting sets of laminates. Each laminate preferablycomprises a carrier member and a cover member with an expandable polymerlayer between the members. Preferably the polymer is heat curable. Eachlaminate contains notches so that the laminates can be interlocked toform a corrugated frame or lattice which may be inserted into a hollowstructure. Upon curing and expansion of the polymer a structural foamresults which is intimately bonded to the spaced side walls of thehollow structure. The hollow structure may, for example, be a pillar inan automobile or could be a hollow panel of a shelving unit.

In an alternative practice of the invention the stiffener could comprisean inverted U connected to an upstanding U with a common leg. An outwardleg at one end of the laminate may extend upwardly beyond the remainderof the laminate so that the laminate could be placed in a lower pillarof a car at the junction of a hollow vertical section with a hollowhorizontal section of the pillar for side impact or joint stiffening.

In a further alternative practice of the invention where the stiffeneris a drop in insert for reinforcing a shelving unit, such as an officefurniture end shelving unit. The laminate may be of straight linearconstruction and simply dropped into the unit so that the laminateextends generally from top to bottom of the hollow panel of the unit. Ina variation the stiffener could be bent such as to form a generallyzig-zag shape.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial side elevational view showing a door frame lower Bpillar of an automobile with a stiffener mounted in place;

FIG. 2 is a side elevational view of the stiffener shown in FIG. 1;

FIG. 3 is a right end elevational view of the stiffener shown in FIGS.1-2;

FIG. 4 is a perspective view of the stiffener shown in FIGS. 1-3;

FIG. 5 is a view similar to FIG. 1 of an alternative form of stiffener;

FIG. 6 is a side elevational view of the stiffener shown in FIG. 5;

FIG. 7 is an end elevational view of the stiffener shown in FIGS. 5-6;

FIG. 8 is a perspective exploded view of the stiffener shown in FIGS.5-7;

FIG. 9 is a front elevational view of a reinforced panel in an officefurniture end shelving unit incorporating a stiffener in accordance withanother alternative of this invention;

FIG. 10 is a top plan view of the panel shown in FIG. 9;

FIG. 11 is a cross-sectional view taken through FIG. 9 along the line11—11;

FIG. 12 is a view similar to FIG. 11 showing the stiffener afterexpansion of the foam;

FIG. 13 is a view similar to FIG. 9 of a panel having an alternativeview of stiffener in accordance with this invention;

FIG. 14 is a top plan view of the panel shown in FIG. 13;

FIG. 15 is a cross-sectional view taken through FIG. 13 along the line15—15;

FIG. 16 is a view similar to FIG. 15 showing the foam in its expandedcondition;

FIG. 17 is a front elevational view of a reinforced panel for a shelvingunit in accordance with still a further embodiment of this invention;

FIG. 18 is a top plan view of the panel shown in FIG. 17;

FIG. 19 is a perspective exploded view of a portion of the stiffenershown in FIGS. 17-18;

FIG. 20 is an elevational view of yet another practice of thisinvention;

FIG. 21 is a cross-sectional view taken through FIG. 20 along the line21—21;

FIG. 22 is a perspective view of a reinforced structural member inaccordance with yet another practice of this invention;

FIG. 23 is an enlarged end elevational view of the structure shown inFIG. 22;

FIG. 24 is a side elevational view of the reinforcement insert shown inFIGS. 22-23;

FIG. 25 is a top plan view of the reinforcement insert shown in FIG. 24;

FIG. 26 is a perspective view of a reinforced structural member inaccordance with an alternative practice of this invention;

FIG. 27 is a perspective view of the reinforcement insert shown in FIG.26;

FIG. 28 is a side elevational view of the reinforcement insert shown inFIGS. 26-27;

FIG. 29 is a top plan view of the reinforcement insert shown in FIGS.26-28;

FIG. 30 is a side elevational view of one of the components of thereinforcement insert shown in FIGS. 26-29;

FIG. 31 is a top plan view of the other of the components of thereinforcement insert shown in FIGS. 26-29;

FIG. 32 is a perspective view similar to FIG. 26 of yet another practiceof this invention;

FIG. 33 is a top plan view of the structure shown in FIG. 32;

FIG. 34 is a side elevational view of the structure shown in FIGS.32-33;

FIG. 35 is a perspective view of the reinforcement insert shown in FIGS.32-34;

FIG. 36 is a cross-sectional view taken through FIG. 35 along the line36—36;

FIG. 37 is a perspective view showing a rein-forced structural member inaccordance with yet another embodiment of this invention;

FIG. 38 is a top plan view of the structure shown in FIG. 37;

FIG. 39 is a cross-sectional view taken through FIG. 38 along the line39—39;

FIG. 40 is a side elevational view of a rein-forced structural member inaccordance with yet another embodiment of this invention;

FIG. 41 is a top plan view of the structural member shown in FIG. 40;

FIG. 42 is a fragmental perspective view showing a reinforcement insertin accordance with a further practice of this invention;

FIG. 43 is a fragmental top plan view showing the reinforcement insertof FIG. 42 mounted in a structural member before expansion of the foam;

FIG. 44 is a view similar to FIG. 43 after expansion of the foam;

FIG. 45 is a perspective view of still yet another form of reinforcementinsert in accordance with this invention;

FIG. 46 is an end elevational view of the insert shown in FIG. 45; and

FIG. 47 is a perspective view of yet another form of reinforcedstructural member in accordance with this invention.

DETAILED DESCRIPTION

The present invention relates to techniques for reinforcing a hollowstructural member having a pair of spaced walls so as to preventbuckling. In general, the techniques include providing a stiffener inthe form of a carrier member having a layer of expandable polymer sothat the stiffener can be readily disposed within the hollow structurebetween the spaced walls. The polymer is disposed for contacting thespaced walls when the polymer is expanded into a rigid structural foam.As will later be described, the stiffener can take various forms so asto maximize the reinforcing ability and the convenience of assembly ofthe stiffener.

FIG. 1 illustrates a portion of a lower B pillar for an automobile doorframe. The B pillar 10 includes a hollow frame having a generallyvertical portion 12 joined to a generally horizontal portion 14. Itwould be desirable to reinforce the pillar at the junction of thevertical and horizontal portions and particularly to provide thereinforcement so as to interconnect the opposite side walls of thepillar 10 for side impact or joint stiffening. One of the side walls 16is illustrated. The other side wall would be parallel to and spaced fromthe illustrated side wall and would have generally the sameconfiguration.

As shown in FIG. 1 a stiffener is located within the hollow structure ofpillar 10. FIGS. 2-4 best illustrate the details of stiffener 18. Asshown therein a layer of polymer 20 is sandwiched between two supportlayers 22,24 to form a trilaminate. One of the layers, such as layer 22,would function as a carrier member while the other layer 24 wouldfunction as a cover member. Preferably, the layers 22,24 are made ofmetal, plastic or fiberglass material and preferably are rigid. Thepolymer layer 20 is preferably made of an expandable resin which uponexpansion forms a structural foam or reinforcement that becomesintimately bonded not only to its carrier and cover members 22,24, butalso to the spaced walls 16 of the hollow structure 10.

Although stiffener 18 may take any suitable shape, it is preferred toform the stiffener with a non-planar shape that provides for addedheight where the vertical portion 12 of pillar 10 meets the horizontalportion 14 and to provide greater length within the horizontal portionitself. By having a non-planar or bent structure it is also possible totake into account the location of holes or any objects that might bewithin the pillar 10.

In the embodiment shown in FIGS. 1-4 the stiffener 18 is in the form ofan upstanding U connected to an inverted U. The inverted U has avertical leg 26 and an opposite vertical leg 28 interconnected byintermediate horizontal portion 30. The upstanding U has a vertical leg32 and shares the common leg 28. Legs 28 and 32 are interconnected byhorizontal portion 34. Each of the remote or outward legs 24,32terminates in an outwardly extending flange 36. In this manner, thevertical leg 32 extends upwardly into the vertical portion 12 of thepillar while the horizontal connecting portion 30 and the vertical leg24 extend outwardly into the horizontal portion 14 of pillar 10. Flange36 extending from leg 24 also extends below connecting portion 34 asbest seen in FIGS. 1-2.

Although FIGS. 1-4 illustrate a stiffener to have a double U shape, suchshape may also be incorporated in other forms such as a W or M or U or Vform.

Any suitable materials may be used for the polymer layer 20 and forlayers 22 and 36. Reference is made to U.S. Pat. Nos. 5,575,526 and5,755,486, as well as application Ser. No. 08/675,173 filed Jul. 3,1996, all of the details of which are incorporated herein by referencethereto. It is preferable to use thin metal layers of sheet/foilthickness for the carrier member 22 and cover member 24. Plastic orfiberglass could also be used. It is also preferable to use a heatexpandable resin for the polymer layer 20 which creates the structuralreinforcement foam upon curing and expansion. Where the invention isused in an assembly line during vehicle production, the heating stepcould be accomplished in an oven conventionally used in such assemblylines without requiring a special added heating step. It is to beunderstood, however, that the invention may also be practiced where, forexample, the resin is chemically cured in order to cause expansion.

FIGS. 5-8 illustrate a preferred variation of the invention wherein thestiffener 40 is made of a plurality of components which areinterconnected to form a corrugated frame or lattice. FIG. 6, forexample, illustrates the stiffener 40 to comprise a pair of laminates 41and 43. The laminates include U-shaped carriers 42,44 each of which hasa layer 46,48 of polymer in its unexpanded condition similar to polymer20. Preferably, a cover member 50,52 is provided over the polymersimilar to the unit 18 described in FIGS. 1-4.

As shown in FIG. 8 each U-shaped laminate 41,43 includes a notch orcutout 56,58 at a connecting portion of the laminate so that the twolaminates 41 and 43 may be interconnected by aligning the notches andthen moving the two laminates together. The laminates 41 and 43 are ofequal width, particularly at the connecting portions. Preferably, thecombined length of the two notches 56,58 is equal to the width of eachlaminate at the connecting portion so that when the two laminates areinterconnected, neither of the laminates extends outwardly of the otherlaminate. In other words, the front faces or walls of the two laminatesare coplanar as are the rear faces or walls. Preferably, each notchextends about half-way into its respective laminate. Each notch has awidth of 7.6 mm.

The corrugated frame 40 would be placed in a hollow structure such asthe pillar 10. The laminate 41 extends into the horizontal portion 14 ofpillar 10, while the laminate 43 extends upwardly into the verticalportion 12 of pillar 10. Upon curing and expansion of the polymer 46,48,the resultant structural foam is intimately bonded to the pair of spacedwalls 16 of pillar 10.

Stiffener 18 or 40 may be placed in the pillar in any suitable mannersuch as by being mounted in place before the two walls 16,16 are securedtogether. The result of incorporating the reinforcement unit in thepillar is to provide a side impact reinforcement or joint stiffeningwhich would be desirable for such structural member.

An example of use for the stiffener in automobiles would be to reinforcea rocker for a lower B pillar and the rear door of an automobile forside impact.

While the invention illustrated in FIGS. 1-8 has been described withrespect to its practice in the automotive industry as a reinforcementfor hollow structures, the invention may also be practiced in otherfields. FIGS. 9-12, for example, illustrate the use of the invention ina hollow panel or side wall 60 which is part of a shelving unit whereinshelves are locked into the end walls of the end unit. As illustrated,panel 60 has a pair of spaced walls 62,62 forming a hollow cavitybetween the walls. The edges of the walls may be secured together attheir flanges 64 by any suitable means such as spot welds 66. Disposedwithin the hollow space between the walls is a stiffener 70. As shown inFIG. 11 stiffener 70 is a drop in insert which comprises a pair ofspaced support members 72,74, similar to the carrier member and covermember of the stiffeners 18 and 40 and which are in contact with walls62,62. Between the members 72,74 is a polymer layer 76, which is shownin FIG. 11 in its unexpanded condition. Upon curing and expansion of thepolymer, the resultant structural foam expands into intimate contactwith the walls 62,62 as illustrated in FIG. 12.

Stiffener 70 could be mounted in the hollow space between walls 62,62 inany suitable manner. Preferably, the stiffener 70 could simply bedropped in from the top before any cap closes the top of the hollowspace between walls 62,62.

As shown in FIG. 9 the stiffener 70 is generally of a straight linearconfiguration in that it extends directly from one end to the other ofthe panel 60 in a straight path. If desired, a plurality of parallelspaced stiffeners 70 may be mounted between walls 62,62.

FIGS. 13-16 show a variation wherein the stiffener 70A is not a straightmember, but rather is shaped or bent in a zig zag type manner. Thisversion provides reinforcement over a greater area between the walls62,62 as compared to the straight structure 70.

FIGS. 17-19 illustrate a preferred variation of the stiffener which isconstructed along the same lines as the stiffener 40 in that a pluralityof laminates are interconnected to form a corrugated frame or lattice.As illustrated, the stiffener 80 comprises a plurality of firstlaminates 82 and a plurality of second laminates 84 which extendcrosswise the laminates 82. Each laminate comprises a pair of supportmembers 86,88 between which is sandwiched the polymer 90 in the mannerpreviously described. The members 86,88 may thus be considered as acarrier member and a cover member for the polymer layer. Laminate 82 isprovided with a plurality of notches 92 to mate with the correspondingnotches 94 in laminate 84. Preferably, the combined length of each setof interlocking notches would be equal to the width of each laminate sothat the resultant corrugated frame is of uniform thickness in that thelaminates terminate coplanar with each other. FIGS. 17-18 show theplacement of the corrugated frame 80 between the walls 62,62 of panel60.

Although the various corrugated stiffeners illustrated herein show theinterconnected laminates to be perpendicular to each other it is to beunderstood that the invention may also be practiced where the laminatesare at a non-perpendicular angle with respect to each other. In suchpractices, the notches would preferably extend at an angle across eachlaminate.

The corrugated frame can readily be dropped in through the open top ofthe panel 60 or trapped between the panels during assembly and act as abrace which, because of its open areas, could be shaped to avoid holesand accommodate any irregularities in the panel.

In the various embodiments, the carrier member and cover member each maybe made, for example, of 0.8 mm of galvaneal steel. The polymer layerbefore curing may be a strip of polymer 6 mm by 75% of the spacingbetween the walls. The spacing between the walls 62,62 may be 25.4 mm.The carrier and cover members may be 0.8 mm thick.

As previously described, the preferred practice of the inventionconsists of a three layer reinforcement made up from two outer layers ofmetal, plastic, or fiberglass and an inner layer of heat curablepolymer. The inner layer would be extruded onto one of the outer layersin a continuous fashion and the other outer layer would be rolled on topof the inner polymer layer. The sandwich would then be sent through aset of roll formers or pinch rollers, notched or trimmed, and then cutto length. The use of pinch rollers or a set of roll formers for thepolymer and support member (one layer or two layers) shapes a crosssection in a continuous manner for the laminate before being cut tolength. Alternatively, the polymer and support member could be stampedto its desired shape by means of a chilled stamping die. The supportmember acts to assist in maintaining part shape and the cooling of thepolymer layer in the stamping die or by ambient or chilled air in theroll forming process also “sets” the part shape. The coincidentalforming of the polymer and support member at the same time differs fromthe current process which involves the separate forming of the polymerlayer and support member and then hand placement of the polymer layeronto the carrier/support member.

Separate pieces would be notched (if appropriate) and cut to lengthwhereby one trilaminate snaps into another trilaminate such that aresidential window grill or corrugated carton partition is formed. FIG.19 shows the simplest configuration which could be used for an officefurniture end shelving unit. See FIG. 17. FIGS. 6-8 shows this approachfor a lower B pillar of a car for side impact or joint stiffening.

In the practice of the invention the two outer layers are rigid enoughto support the diaphragms or stiffeners such that they retain theirshape during forming, handling, and heat curing of the inner polymerlayer and that they constrain the polymer such that the polymer expandsin the plane of the laminate and consequently bonds to the walls of thehollow section to be reinforced. The interlocking nature of laminatesallows for internal, self-supporting bulkheads to be placed in key areasof the hollow sections such that premature buckling of the parent ormain hollow sections does not take place under applied loads.

A trilaminate is preferably formed by an in-line extrusion roll formingprocess such that trimmed, bent, notched, and cut lengths can befabricated into interlocking support shapes. The interlocking sectionswhether they be straight or bent can be used to reinforce hollowsections in key or critical areas thereby minimizing material usagethrough effective placement of the interlocking bulkheads or diaphragms.This approach lends itself to application in difficult areas to bereinforced. The interlocking laminates prevent thin section wallbuckling due to wall stresses caused by bending or axial loading. Also,another important feature is that the two outside laminate skins orlayers constrain the polymer towards bonding one side of the section tothe other plus bonding the laminate layers to themselves. Theinterlocking trilaminate is another means of tying the side walls of athin gage section together apart from filling a section solid with foamor lining the interior walls of a hollow section with a polymerlaminate.

In practice, when forming the various stiffeners, a layer of polymerresin would be extruded onto the carrier member. In the broad practiceof the invention the unit could include a laminate structure comprisingonly the carrier member and layer of resin. In the preferred practice,however, the cover member is added on the exposed side of the resinlayer to sandwich the layer between the two support members. By havingtwo support members the polymer is constrained and upon expansion of thefoam the members direct the foam into bonding contact with the thinwalls of the hollow structure. Where the stiffener is formed in an inline process the laminate structure would then be chilled at, forexample, a temperature in the range of 0° to −40° F. After chilling anynecessary trimming or notching could be done using any suitabletechniques such as die cutting or the application of a water jet. Thelaminate would then be cut to length and where necessary would be bentto its desired shape. Where the unit is a corrugated frame theindividual laminates would then be interlocked with each other at thenotches formed in the connecting portions of the laminate.

FIGS. 20-21 show a variation of the invention. As shown therein, thetrilaminate stiffener 96 is in the shape of a horseshoe placed over thepin 98 and seated on the bottom of the rail 99. Rail 99 may includedimples 97 which penetrate the foam layer to hold the stiffener 96 inplace. Preferably the stiffener 96 is made in-line, extruded, die cut inits flat condition and then bent to the final profile.

As is apparent one aspect of the invention involves a stiffener forreinforcing a hollow structure having a pair of spaced walls. Thestiffener comprises a carrier member with a layer of expandable polymeron the carrier member and a cover member on the polymer layer. Thestiffener is of non-linear shape, such as a W, M, U or V shape or someother irregular shape.

FIGS. 22-47 relate to variations of the previously described techniques.In the following description reference will be made to variousstructural arrangements and materials. It is to be understood that thesedetails are considered exemplary of various practices of the inventionand that the various shapes, relationships and materials disclosed inprior practices may also be utilized in the various practices of FIGS.22-47.

FIGS. 22-25 illustrate one practice of this invention which involves thereinforcement of a channel shaped structural member 110 by means of adrop in reinforcement insert 112. In the illustrated embodimentstructural member 110 is a truck pickup floor beam. Reinforcement insert112 is in the form of a convoluted trilaminate which functions as aninternal spacer to maintain the cross sections during gross beamdeflection. This approach is similar to the convoluted trilaminatepreviously described, particularly for furniture application except thatin the prior embodiment the trilaminate is loaded in tension in thenarrow direction. In the embodiment illustrated in FIGS. 22-23, for thepickup beam, for example, the trilaminate reinforcement 112 is loaded incompression in the short or narrow direction. The trilaminate wouldcomprise a central layer 111 of structural foam with an outer layer 113functioning as a carrier and/or cover or support layer on each side ofthe structural foam as described in the prior application.

As illustrated the convoluted shape need not be uniform in its degree ofconvolution. Thus, for example, the central portion of the reinforcementinsert 112 could have its bent sections spaced closer together than atthe end portions. This is best shown in FIGS. 22 and 25.

FIGS. 26-31 illustrate a further practice of this invention. As showntherein the reinforcement insert 114 or trilaminate is mounted in thechannel of a front rail 116 of an automotive vehicle behind the frontwheels and underneath the tow board. This trilaminate reinforcementinsert 114 is in the form of a curved generally vertical wall 122 havingflat sides and which runs in the area of maximum vertical concurvaturein the side view on the bottom of rail 116, as shown in FIG. 26. Indiscrete sections or locations along the trilaminate length it would bedesirable to install horizontal bulkheads 118 which are also in the formof trilaminates cut to fit the vertical wall 122. FIGS. 30-31, forexample, show the vertical wall 122 to have a slot 117 and the bulkheador horizontal wall 118 to have a slot 119. The vertical wall 122 andhorizontal bulkhead 118 are thus joined together by engagement at theslots 117 and 119. Alternatively, the bulkheads 118 could be located bymeans of tabs that key into holes or slots 120 in the vertical walls 122of the main component trilaminate insert 114 as shown, for example, inFIGS. 35-36. The horizontal bulkheads 18 would function to preventlateral buckling of the rail section in a local area. The main verticalreinforcement 122 is used to prevent buckling in the rail vertical orside view direction. The horizontal bulkhead 118 forms a cross brace forthe rail section when it is slipped into the vertical member 122.

The various components of reinforcement insert 114 may be custom shapedin accordance with the end use. For example, as illustrated the verticalmember 122 may include an arcuate wall 115 which may be semi-cylindricalin shape to clear a pin located in the structural member so that theassembled rail components could be welded to each other.

The various figures also illustrate a clearance hole 121 in the bulkheador horizontal member 118 for the fastener.

FIG. 29 best illustrates a practice of the invention where the thicknessof the vertical member 122 varies from one end to the other. Thus, forexample, the end on the left hand portion of FIG. 29 is twice as thickas the remote end on the right hand portion with the thickness uniformlytapering from one end to the other. The laminate 122 might thus be 8 mmthick at one end and 4 mm thick at the other end.

FIGS. 32-36 illustrate a practice of the invention very similar to thatof FIGS. 26-31 except that in FIGS. 32-36 the vertical member 122 is inthe form of vertical pleats which run in the area of maximum verticalcurvature in the side view of the bottom rail 116 as shown in FIG. 34.The main function of the convolutions of reinforcement insert 114 is tostabilize the vertical web from buckling in the lateral or horizontaldirection. A vertical wall will buckle under a smaller compressive loadthan a wall that has a series of vertical stiffeners or convolutes. Thisalso applies to the web trapped between the two horizontal bulkheads118,118. At this location the convolutes act as miniarches to supportthe horizontal bulkheads and consequently the main rail section.

FIGS. 37-39 represent an application for non-automotive use in which arecessed floor 124 is capped with a piece of sheet metal 126 that ishemmed over the four perimeter flanges 128 around the recessed area toform a pan. This part may be used, for example, for computer roomsub-floors to isolate computer equipment from cabling underneath. Thus,the pan 126 includes, in effect, creates a pit 130 in the recessed floor124 to accommodate electrical wiring and cooling equipment. Theassembled pans 126 are supported by a metal grillage and the pans aredropped into the grillage and hung from their flanges. The currentmethod to reinforce the pans is to fill the pans with concrete, but thismethod yields a heavy part which is difficult to install and messy tofabricate. In accordance with the invention the concrete is replacedwith a trilaminate partition 132 formed by interlocked supports 133,135to form a grid. As best shown in FIGS. 37 and 39 supports 133 and 135terminate in ends 134 having a horizontal lower surface for placement onhorizontal pans 126. Inwardly of ends 134, each support 133,135 isdownwardly inclined to the center of partition 132. This arrangementassures a self centering of partition 132 in pan 126 because the spacingbetween the opposite horizontal ends 134 from the points where the endsbegin to taper would be equal to the spacing between opposite sides ofpan 126. Additionally, the downward taper of supports 133,135 means thatthere is an increased amount of reinforcement into pit 130.Alternatively, each support 133,135 may have its ends 134 compriseflanges of otherwise rectangularly shaped supports, rather than taperedsupports. FIG. 39 illustrates the supports to terminate a distance abovefloor 124. This spacing and the tapered lower edges of supports 133,135assures providing sufficient room in pit 130 to accommodate wiring, etc.An alternative would be to form the minibeams into interlocking archesthat are bearing on the bottom of the pit. Prior embodiments illustratevarious manners of forming a partitioned reinforcement. Thus, thecomputer floor module 24 is effectively supported.

FIGS. 40-44 illustrate a variation of a stiffener 136 which is inlattice form comprising a plurality of first laminates 138 and aplurality of second laminates 140 extending cross wise to the laminates138. Each laminate comprises a pair of outer support members 142,144between which is sandwiched the polymer 146. Each laminate 138,140 isprovided with a plurality of notches 148,150 so that the notches maymate with each other to create an interlocked structure forming thereinforcement 136. FIGS. 43-44 show the laminate structure between walls152,154 of a member which is intended to be reinforced. FIG. 43 showsthe arrangement before the polymer 46 has expanded, while FIG. 144 showsthe polymer 146 expanded into a structural foam intimately bonded toeach side wall 152,154.

In accordance with a further feature of this invention mechanicalstaples 156 are used to keep the trilaminate structure together andallow the polymer 146 to expand in the plane of the laminate in order totie the two opposing sides 142,144 together and ultimately to tie thesides 152,154 together. The staples keep the metal sides 142,144 frombulging and moving laterally and force the polymer expansion to theopposing walls 152,154 that are to be reinforced and tied together.

FIGS. 45-46 show a further reinforcement insert 158 in accordance withanother embodiment of this invention. Such insert might be used, forexample, to reinforce the lower B pillar of an automobile. As showntherein, one trilaminate member 160 would slide into an elongated notch162 of the perpendicular trilaminate member 164. If desired, surfaceinterruptions, such as holes 166 or further notches 168 or tapers 170,may be provided on the laminate members to accommodate the shape of thestructural member being reinforced.

FIG. 47 shows yet another practice of this invention wherein thereinforcement insert 172 is in the form of a tube 174 completelyperipherally wrapped with polymer 176. For example, the tube 174 couldbe of 0.8 mm cold rolled steel wrapped on all four sides with thepolymer. The wrapped tube could then be inserted into an A pillarsection and cured under E coat oven conditions. This form of laminate isa two-layer laminate rather than a trilaminate.

It has been proposed by others to reinforce an A pillar cross-section bymeans of an aluminum extrusion cross or plus sign tipped with anadhesive polymer. Such arrangement has various drawbacks when using thisform of aluminum cross like structure. For example, the part has to beextruded in a straight section with the curvature being a secondaryforming step. The cross would be very difficult to bend because it isnot a tube and it could not hold its shape well and would distort. Thepart could not be extruded in a metal thickness less than 1.5 mm andmost preferably 2.0 mm. The larger the section the more aluminum isrequired thus making this approach less competitive. In addition, inorder to make the extrusion effective the webs, flats or walls ofaluminum have to be normal or 90° to the wall or roof which they arebracing. Any off angle position would cause the reinforcement to slipfrom under their support. The polymer could not be strong enough toresist this underpinning failure. There would also be a problem withsnaking a straight edge of the aluminum extrusion between holes. Toclear holes the extrusion would have to be notched which results inadditional cost. Since most of the automotive sections are neverconstant over their length additional edge polymer would have to be usedto compensate for widening gaps. This could result in trimming thelength of the part to fit or result in loss of reinforcing efficiencysince the reinforcement could slip or rotate within in the main hollowcross section. Once the extrusion dies are set, part changes result intool changes and loss of time, although aluminum dies are not expensive.

What is claimed is:
 1. A stiffener for reinforcing a hollow structurehaving a pair of spaced walls, said stiffener comprising a laminateincluding a carrier member, a layer of expandable polymer on saidcarrier member, said laminate being of non-linear shape, said laminateincluding a cover member on said layer of expandable polymer, saidnon-linear shape being an upstanding U connected to an inverted U, saidupstanding U having a pair of vertical legs and a horizontal connectingsection, said inverted U having a pair of upstanding legs and ahorizontal connecting section, one of said legs of said upstanding Ubeing a leg common to said inverted U, the other of said legs of saidupstanding U being an outward leg and the other of said legs of saidinverted U being an outward leg, and one of said outward legs extendingabove the remaining of said legs and above said horizontal connectingsections.
 2. The stiffener of claim 1 wherein said carrier member andsaid cover member are rigid.
 3. The stiffener of claim 1 wherein theother of said outward legs terminates below the remaining of said legsand below said horizontal connecting sections, and said polymer beingheat expandable.
 4. The stiffener of claim 3 in combination with anautomobile pillar having an elongated vertical portion connected at ajunction to an elongated horizontal portion, and said stiffener beinglocated at said junction.